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Abstract:

A winch apparatus (10) comprises first and second drum assemblies (12,
14) each defining a discontinuous drum contact surface for engaging a
common spoolable medium (50), wherein the first and second drum
assemblies (12, 14) are configured to rotate about respective first and
second axes of rotation (24, 26) which are inclined relative to each
other. In one disclosed embodiment the drum assemblies (12, 14) are
intermeshed in a general axial direction.

Claims:

1. A winch apparatus comprising first and second drum assemblies each
defining a discontinuous drum contact surface for engaging a common
spoolable medium, wherein the first and second drum assemblies are
arranged to rotate about respective first and second axes of rotation
which are inclined relative to each other.

2. A winch apparatus according to claim 1, configured as a capstan winch
apparatus.

3. The winch apparatus according to claim 1, wherein the first and second
axes of rotation are inclined relative to each other in two reference
planes.

4. The winch apparatus according to claim 3, wherein the two reference
planes are mutually perpendicular.

5. The winch apparatus according to claim 1, wherein the first and second
axes of rotation are inclined at least one of axially and radially
relative to each other.

6. The winch apparatus according to claim 1, wherein each drum contact
surface is aligned generally parallel to an associated drum axis of
rotation such that the drum contact surfaces of the respective first and
second drum assemblies are also inclined relative to each other to the
same extent as the first and second axes of rotation.

7. The winch apparatus according to claim 1, wherein the first and second
drum assemblies are configured to engage a wrapped intermediate portion
of a spoolable medium, such that end portions of the spoolable medium on
either side of the intermediate wrapped portion extend outwardly from the
winch apparatus to define an outboard end portion and an inboard end
portion.

8. The winch apparatus according to claim 7, comprising a tensioner
arrangement for applying a degree of tension to at least one end portion
of a spoolable medium.

9. The winch apparatus according to claim 1, wherein the relative
inclined alignment of the first and second axes of rotation of the drum
assemblies is arranged to permit the respective drum contact surfaces to
cooperate to manipulate an associated spoolable medium to follow a
predefined path.

10. The winch apparatus according to claim 9, wherein the predefined path
is helical.

11. The winch apparatus according to claim 1, wherein the angle of
relative inclination of the first and second axes of rotation is fixed.

12. The winch apparatus according to claims 1, wherein the angle of
relative inclination is adjustable.

13. The winch apparatus according to claim 1, wherein the angle of
relative inclination of the first and second axes of rotation is selected
to be in the region of 1 to 3 degrees.

14. The winch apparatus according to claim 1, wherein for each single
wrap of a spoolable medium, one portion of the spoolable medium wrap
engages the drum contact surface of the first drum assembly, and the
remaining portion engages the drum contact surface of the second drum
assembly.

15. The winch apparatus according to claim 1, wherein the drum assemblies
overlap in an axial direction.

16. The winch apparatus according to claim 1, wherein the drum assemblies
overlap in a radial direction.

17. The winch apparatus according to claim 1, wherein the drum assemblies
intermesh each other.

18. The winch apparatus according to claim 1, wherein each drum assembly
comprises a plurality of support elements which collectively define the
respective drum contact surfaces.

19. The winch apparatus according to claim 18, wherein the support
elements are elongate.

20. The winch apparatus according to claim 18, wherein the support
elements are circumferentially arranged about a respective axis of
rotation of the drum assemblies.

21. The winch apparatus according to claim 18, wherein each support
element comprises an individual support surface arranged to define a
discrete portion of a respective drum contact surface.

22. The winch apparatus according to claim 21, wherein the individual
support surface of one or more support elements defines an arc shape.

23. The winch apparatus according to claim 18, wherein each support
element defines an are shape support surface, wherein the combined arc
angle of the support elements of a single drum assembly extends
approximately 360 degrees.

24. The winch apparatus according to claim 18, wherein a pair of adjacent
support elements define respective arc shaped surfaces, wherein facing
edges of the adjacent arc shaped surfaces are arranged tangentially to
each other.

25. The winch apparatus according to claim 18, wherein the support
elements are rigidly mounted within the respective drum assemblies.

26. The winch apparatus according to claim 18, wherein the support
elements are adjustably mounted within a respective drum assembly.

27. The winch apparatus according to claim 18, wherein the support
elements are arranged relative to each other to create a discontinuous
drum contact surface, with adjacent support elements spaced from each
other to define a gap therebetween.

28. The winch apparatus according to claim 18, wherein the support
elements of each drum assembly interleave each other.

29. The winch apparatus according to claim 27, wherein the support
elements of one drum assembly are positioned in the gaps between the
support elements on the other drum assembly.

30. The winch apparatus according to any preceding claim 1, wherein the
drum assemblies are arranged on separate support shafts.

31. The winch apparatus according to claim 1, wherein the drum assemblies
are arranged on a common support shaft.

32. The winch apparatus according to claim 31, wherein one or both of the
drum assemblies are offset relative to the support shaft to provide the
relative inclination between the first and second axes of rotation.

33. The winch apparatus according to claim 1, wherein the drum assemblies
are arranged to be offset from each other in a radial direction to be
positioned side by side.

34. The winch apparatus according to claim 1, comprising a drive
arrangement configured to drivingly rotate both drum assemblies.

35. The winch apparatus according to claim 34, wherein the drive
arrangement is configured to synchronously drive both drum assemblies.

36. The winch apparatus according to claim 34, wherein the drive
arrangement comprises a single drive assembly configured to drive both
drum assemblies

37. The winch apparatus according to claim 34, wherein the drive
arrangement comprises a first drive apparatus associated with the first
drum assembly, and a second drive apparatus associated with the second
drum assembly.

38. The winch apparatus according to claim 34, wherein the drive
arrangement functions to provide braking to one or both drums.

39. The winch apparatus according to claim 1, wherein the surface of one
or both of the drum contact surfaces is configured such that the
coefficient of friction between the respective surfaces and a spoolable
medium is less than the coefficient of friction between individual
components of the spoolable.

40. A method for establishing a tension gradient within a spoolable
medium, comprising: providing first and second drum assemblies each
defining a discontinuous drum contact surface; wrapping a portion of the
spoolable medium around the contact surface of both the first and second
drum assemblies; and rotating both the first and second drum assemblies
about respective first and second axes of rotation which are inclined
relative to each other.

41. A winch system comprising a winch apparatus including first and
second drum assemblies each defining a discontinuous drum contact surface
for engaging a common spoolable medium, wherein the first and second drum
assemblies are arranged to rotate about respective first and second axes
of rotation which are inclined relative to each other.

42. A winch apparatus comprising first and second drum assemblies each
including a plurality of support elements for engaging a common spoolable
medium, wherein the support elements of each drum assembly interleave
each other.

43. The winch apparatus according to claim 42, wherein the drum
assemblies are arranged to rotate about respective first and second axes
of rotation which are inclined relative to each other.

Description:

FIELD OF THE INVENTION

[0001] The present invention relates to a winch apparatus, and in
particular, but not exclusively, to a capstan style winch apparatus.

BACKGROUND TO THE INVENTION

[0002] Winches are used in many applications to move payloads via
spoolable media, such as metal, synthetic or fibre cables, wires and
ropes. Typically, a winch includes a drum or spool around which a
spoolable medium is wound, wherein rotation of the drum permits spooling
of the medium.

[0003] In some species of winch the drum also acts to store the spoolable
medium, with the medium be arranged in single or multiple wraps and
layers between end flanges of the drum. In such winch species, however,
the spoolable medium may be subject to significant radial crushing
forces, particularly in circumstances where large payloads are involved
and thus significant tensions are applied to the spoolable medium.
Further, in some applications it may be necessary to store the medium in
a high tension state, which may reduce the life span of the medium
through fatigue, excessive strains, hysteresis and the like. Furthermore,
storage of the spoolable medium on a drum typically requires the use of
complex fleeting arrangements to ensure that the medium is arranged in
suitable wraps and layers.

[0004] In other species of winch the drum is used only to apply a force to
a spoolable medium, with the spoolable medium being stored separately,
for example in a basket, on a separate spool or the like. The force
applied by the drum is typically either a pulling force to pay in a
spoolable medium, or a controlled releasing force to permit controlled
paying out of a spoolable medium while under load, for example while
connected to a payload. In such winch species, which may include capstan
or windlass winches, an intermediate portion of a spoolable medium is
wrapped around the drum a number of times such that an outboard side of
the spoolable medium extends from the drum to engage a payload, and an
inboard side of the spoolable medium extends to storage. Under loaded
conditions the drum functions to reduce the tension in the spoolable
medium from a high tension condition in the outboard side, to a lower
tension condition in the inboard side of the spoolable medium, thus
permitting the spoolable medium to be stored in a favourable low tension
state. In view of this tension reduction functionality, such winch
species are often called detensioning units. In use, the drum establishes
a tension gradient in the spoolable medium, which may be defined by the
capstan friction equation:

[0008] In existing winch devices the tension gradient may not be evenly
distributed across the spoolable medium in contact with the drum, which
may result in non-uniform tension reduction with possible adverse effects
on the medium, such as variable strain distribution and the like.

[0009] In such capstan style winch species, arrangements are typically
made to ensure that the spoolable medium follows a defined path around
the drum to ensure appropriate separation between adjacent wraps, provide
appropriate take off points for both outboard and inboard sides, prevent
piling or bunching at flanged ends of the drum, and the like. These
arrangements may include the use of grooves or flutings on the surface of
the drum, the use of knives or fleeting rings and the like. GB 2 009 077,
GB 1 425 016 and WO 00/10903 each discloses arrangements in which drum
grooves are utilised.

[0010] However, such arrangements for suitably handling a spoolable medium
along a desired path may involve complex mechanisms, which may be
expensive and subject to failure. Further, existing arrangements may not
adequately handle features of a spoolable medium, such as splices,
connectors, sockets and the like. Also, existing arrangements, such as
knives or fleeting rings, may result in adverse twisting of the spoolable
medium, and can increase the frictional forces applied to the medium,
which may result in abrasion or other damage which may affect mechanical
integrity.

SUMMARY OF THE INVENTION

[0011] According to a first aspect of the present invention there is
provided a winch apparatus comprising first and second drum assemblies
each defining a discontinuous drum contact surface for engaging a common
spoolable medium, wherein the first and second drum assemblies are
configured to rotate about respective first and second axes of rotation
which are inclined relative to each other.

[0012] The winch apparatus may be configured to function as a detensioning
device for use in reducing tension within a spoolable medium. The winch
apparatus may be configured as a capstan winch apparatus.

[0013] The first and second axes of rotation may be inclined relative to
each other in a single reference plane. The first and second axes may be
inclined relative to each other in two reference planes, such as two
mutually perpendicular reference planes. The first and second axes of
rotation may be inclined axially and/or radially relative to each other.
The first and second axes of rotation may be inclined relative to each
other so as to be in non-parallel relation. For example, the first and
second axes of rotation may be inclined to intersect each other at an
intersection angle. The first and second axes of rotation may be arranged
eccentrically relative to each other. In some embodiments the first and
second axes of rotation may be laterally offset from each other.

[0014] Each drum contact surface may be aligned generally parallel to an
associated drum axis of rotation. In this arrangement the drum contact
surfaces of the respective first and second drum assemblies may also be
inclined relative to each other to the same extent as the first and
second axes of rotation.

[0015] In use, the first and second drum assemblies may be configured to
permit a common spoolable medium to be wrapped around the respective drum
contact surfaces, such that rotation of each drum assembly may apply a
force to the spoolable medium. The winch apparatus may therefore be used
to pay in the spoolable medium to, for example apply a pulling force on
an attached payload, and/or to permit controlled paying out of the
spoolable medium, for example to deploy an attached payload.

[0016] The first and second drum assemblies may be configured to engage a
wrapped intermediate portion of a spoolable medium, such that end
portions of the spoolable medium on either side of the intermediate
wrapped portion may extend outwardly from the winch apparatus. One end
portion may be defined as an outboard end portion, and the other end
portion may be defined as an inboard end portion. This arrangement may
permit the winch apparatus to function as a capstan type winch. For
example, rotation of the first and second drum assemblies may apply a
tension gradient along the length of the spoolable medium in contact with
the winch apparatus. This tension gradient may be determined in
accordance with the capstan friction equation:

[0021] Thus, the tension gradient may be determined as a function of the
wrap contact angle and co-efficient of friction between the spoolable
medium and the contact surfaces. In normal use, one end portion of the
spoolable medium may be at a higher tension than the other end portion.
One end portion, such as a high tension portion (which may be an outboard
end portion), may extend to engage a payload, and the other end portion,
such as a low tension portion (which may be an inboard end portion), may
be suitably stored, for example on a spool, in a basket or the like.

[0022] In one embodiment the winch apparatus may be provided in
combination with, or comprise, a tensioner arrangement, which may
function to apply a degree of tension to at least one end portion of a
spoolable medium. For example, a tensioner arrangement may be configured
to apply tension to a low tension portion (for example an inboard end
portion) of a spoolable medium which extends from the winch apparatus.
The tensioner arrangement may be configured to permit greater control
over the achievable tension in a high tension portion of the same
spoolable medium. For example, a tensioner device may be utilised to
increase tension in a low tension end portion, such that a tension
gradient applied by the winch apparatus may accommodate a higher tension
in a high tension end portion (in accordance with the capstan friction
equation defined above). The tensioner device may comprise a further
winch, such as a drum winch, traction winch, winch apparatus according to
the present invention or the like. The tensioner device may comprise a
track tensioner. In some situations, such as static situations a
tensioner device may be configured not to apply any tension. In other
situations, such as in dynamic situations, a tensioner device may be
configured to apply a degree of tension.

[0023] The relative inclined alignment of the first and second axes of
rotation of the drum assemblies may permit the respective drum contact
surfaces to cooperate to manipulate an associated spoolable medium to
follow a predefined path, such as a predefined helical path. This
predefined path may advantageously permit adjacent wraps of a spoolable
medium to be preferentially aligned during rotation of the drum
assemblies, for example to be arranged and retained in non-contact
relationship with each other, with a preferred separation gap or the
like. Furthermore, the relative inclined alignment of the axes of
rotation may permit a spoolable medium to exit or enter the winch
assembly at a desired and/or constant location. This preferred control
over the path of an associated spoolable medium may eliminate the
requirement to provide additional control equipment, such as knives,
fleeting arrangements, flutings or the like, and thus avoid the
disadvantages of such arrangements, for example disadvantages associated
with costs, complexity, maintenance, increased weight and the like.

[0024] The angle of relative inclination of the first and second axes of
rotation may be fixed. Alternatively, the angle of relative inclination
may be adjustable.

[0025] The angle of relative inclination of the first and second axes of
rotation may be selected to influence or provide a predetermined path,
such as a predetermined helical path of a spoolable medium, for example
the number of wraps, spacing between individual wraps or the like. The
angle of relative inclination of the axes may be selected in accordance
with the type of spoolable medium, which may include a metal or synthetic
or fibre wire, cable, rope or the like.

[0026] In some arrangements the angle of relative inclination of the axes
of rotation may define a pitch angle of one or more wraps of a spoolable
medium.

[0027] The angle of relative inclination of the first and second axes of
rotation may be selected to be in the region of, for example, 0.1 to 20
degrees, such as between 0.5 and 10 degrees. In some embodiments the
angle of relative inclination may be selected to be in the region of 1 to
3 degrees. In one embodiment the relative angle of inclination may be
selected to be in the region of 1.8 degrees.

[0028] The drum assemblies may be arranged such that, in use, a spoolable
medium engages the drum contact surface of both the first and second drum
assemblies. The drum assemblies may be arranged such that, in use, a
spoolable medium engages a portion of the drum contact surface of both
the first and second drum assemblies. In one embodiment the drum
assemblies may be arranged such that, in use, for each single wrap of a
spoolable medium, one portion, such as a half portion, of the spoolable
medium wrap engages the drum contact surface of the first drum assembly,
and the remaining portion, such as the other half portion, engages the
drum contact surface of the second drum assembly. This arrangement, in
combination with the relative inclination of the first and second axes of
rotation, may permit a predefined path of the spoolable medium to be
achieved. This arrangement may also permit the loading on the winch
apparatus to be split between the first and second drum assemblies, and
any associated supporting arrangements.

[0029] The discontinuous drum contact surfaces (which may be provided by
separate support elements as defined below) may permit a discretised
tension gradient to be applied across the length of a spoolable medium in
contact with said surfaces. For example, the discontinuous drum contact
surfaces will provide intermittent contact with a spoolable medium, such
that discrete portions of a complete tension gradient across the complete
length of the spoolable medium will be achieved at those individual
discrete locations of contact. This arrangement may permit more control
over the tension gradient in the spoolable medium. Furthermore, this
arrangement may permit a required tension gradient to be ensured over a
minimum length of a spoolable medium. Accordingly, high resolution
de-tensioning may be achieved by applying many small points of contact
providing a proportionally small variance in tension differential. Thus,
changes in length, relative movement, work and the like are minimised to
mitigate frictional heat generated in the spoolable medium. Tension may
therefore be removed or added in many small accurately controlled linear
steps as opposed to a low quantity of large steps as present in prior art
systems. This arrangement provides a kind method of working the spoolable
medium to provide longer life and operate the spoolable medium in its
natural form without applying excessive external forces.

[0030] The discontinuous contact surface may facilitate cooling of the
spoolable medium when in use, for example by permitting increased flow of
a coolant, such as air, around the spoolable medium, for example between
individual support elements. Additionally, the discontinuous contact
surface may facilitate drainage, for example where the spoolable medium
is retrieved from a liquid environment, such as a sea environment. For
example, in embodiments where a discontinuous surface is provided by
multiple spaced apart support elements, drainage may be permitted through
the gaps between adjacent support elements.

[0031] Each drum assembly may comprise a plurality of support elements
configured to collectively define the respective drum contact surfaces.
The support elements may be elongate. The support elements may be
arranged parallel with the respective axes of rotation. The support
elements may be circumferentially arranged about a respective axis of
rotation of the drum assemblies. Each support element may comprise an
individual support surface arranged to define a discrete portion of a
respective drum contact surface. The individual support surface of one or
more support elements may define an arc shape. In one arrangement the
individual support surface of one or more support elements may define a
circular arc shape. The individual support surface of one or more support
elements may extend for a defined arc angle, wherein the arc angle is
defined by the central angle formed by the end points of the arc. Each
support element may define an arc shape support surface, wherein the
combined arc angle of the support elements of a single drum assembly may
extend 360 degrees. This arrangement may permit a preferential support of
a spoolable medium over the collective drum contact surfaces, which may
prevent any kinking or the like of the spoolable medium across any edge
regions of the support elements. This arrangement may also permit a
preferential support of a spoolable medium to be permitted while
achieving a maximum tension gradient within the spoolable medium by
maximising the available wrap angle.

[0032] A pair of adjacent support elements may define respective arc
shaped surfaces, wherein facing edges of the adjacent arc shaped surfaces
are arranged tangentially to each other. This arrangement may permit a
spoolable medium to extend tangentially between adjacent support
elements, thus achieving complete contact with each individual surface
and preventing any adverse kinking or the like of the spoolable medium as
it leaves one support surface and arrives at the other support surface.

[0033] The support elements may be arranged relative to each other to
create a discontinuous drum contact surface. Adjacent support elements
may be spaced from each other to define a gap therebetween. This
arrangement may provide the respective discontinuous drum contact
surfaces. Providing support elements with gaps therebetween may permit
the support elements to be positioned to define a desired effective drum
diameter, for example which is appropriate to the particular spoolable
medium, and at the same time provide the necessary overall wrap angle to
achieve a suitable tension gradient while minimising the actual contact
surface area. That is, the support elements may be arranged within an
individual drum assembly to provide an effective drum diameter, with an
overall reduced contact surface.

[0034] The provision of gaps between support elements may provide
advantages in terms of cooling, drainage and the like, as identified
above.

[0035] The support elements may be rigidly mounted within the respective
drum assemblies. Such rigid mounting may provide a fixed effective drum
diameter. Alternatively, the support elements may be adjustably mounted
within a respective drum assembly, which may permit an effective drum
diameter to be adjusted. This may permit use of the winch apparatus with
different spoolable media. This arrangement may also permit the support
elements to be adjusted for compensation requirements, for example to
compensate for any movement of the entire winch apparatus relative to a
datum point. This may have benefit in offshore applications, where the
winch apparatus may be used to deploy or retrieve payloads into or from
the sea.

[0036] The support elements may be formed separately and subsequently
mounted within the respective drum assemblies, for example by use of
mechanical fasteners, welding or the like. Alternatively, the support
elements may be provided as integral components of the respective drum
assemblies. For example, the support elements may be integrally cast with
the respective drum assemblies.

[0037] Each drum assembly may comprise a flange member configured to
support a plurality of support elements, for example at respective end
regions of the support elements, or respective intermediate portions of
the support elements. Each drum assembly may comprise two flange members
configured to support opposite end regions of each associated support
element. This arrangement may define a cage structure, such as a
generally cylindrical cage structure.

[0038] The drum assemblies may be arranged to overlap in an axial
direction. This may permit a spoolable medium to extend across, for
example generally laterally or transversely of, both axes of rotation to
engage the respective drum contact surfaces without requiring any imposed
direction change to move from one surface to the other.

[0039] The drum assemblies may be arranged to overlap in a radial
direction. The drum assemblies may be configured to be intermeshed
relative to each other. In one embodiment each drum assembly may comprise
a plurality of support elements arranged to define gaps therebetween,
wherein the support elements of one drum assembly are configured to be
positioned in the gaps between the support elements on the other drum
assembly, and vice versa. Accordingly, the support elements of each drum
assembly may intermesh or interleave each other. This arrangement may
permit the advantages of the present invention, for example in relation
to providing a predefined path for a spoolable medium, to be achieved
while presenting a minimal footprint.

[0040] The drum assemblies may be arranged on separate support
arrangements, such as separate support shafts. The separate support
shafts may be appropriately arranged to provide the relative inclination
between the first and second axes of rotation.

[0041] The drum assemblies may be arranged on a common support
arrangement, such as a common support shaft. For example each drum
assembly may be arranged to be rotatable about a common support shaft. In
this arrangement one or both of the drum assemblies may be offset
relative to the support shaft to provide the relative inclination between
the first and second axes of rotation. For example, one or both of the
drum assemblies may be arranged on an offset portion of the support
shaft, mounted on an offset bearing arrangement or the like.

[0042] The drum assemblies may be arranged to be offset from each other in
a radial direction, for example side by side. In this arrangement the
drum assemblies may be provided in non-intermeshing relation. This
arrangement may permit smaller drum assemblies to be utilised.

[0043] The winch apparatus may comprise a drive arrangement configured to
drivingly rotate both drum assemblies. The drive arrangement may be
configured to synchronously drive both drum assemblies. This arrangement
may assist to ensure that the contact between the respective drum contact
surfaces and a spoolable medium is optimised. Additionally, this may
prevent slippage of the spoolable medium relative to one or both the drum
contact surfaces. Also, this arrangement may minimise any axial rotation
of the spoolable medium.

[0044] The drive arrangement may comprise a single drive assembly
configured to drive both drum assemblies, for example via a mechanical
transmission arrangement, such as a belt drive, chain drive, gear train
or the like. Alternatively, the drive arrangement may comprise a first
drive apparatus associated with the first drum assembly, and a second
drive apparatus associated with the second drum assembly. In this
embodiment the drive arrangement may comprise a controller configured to
permit common control of the first and second drive apparatus.

[0045] The drive arrangement may function to provide braking to one or
both drums.

[0046] The apparatus may comprise a braking arrangement configured to
provide braking to one or both drums. The braking arrangement may
comprise an electrical braking arrangement friction braking arrangement
of the like.

[0047] The surface of one or both of the drum contact surfaces may be
configured such that the coefficient of friction between the respective
surfaces and a spoolable medium is less than the coefficient of friction
between individual components of the spoolable medium, such as braids,
strands or the like. This may assist in achieving a desired low tension
gradient in the spoolable medium. One or both of the drum contact
surfaces may comprise a coating, such as a chrome coating, ceramic
coating or the like.

[0048] The winch apparatus may be configured for use with, or may
comprise, a spoolable medium storage arrangement. The storage arrangement
may comprise a spool, basket or the like.

[0049] The winch apparatus may itself be compensated and/or may be
configured for use with, or may comprise, a compensator arrangement. The
compensator arrangement may comprise a heave compensator arrangement, for
example to compensate for heaving motion of an offshore vessel upon which
the winch apparatus is located.

[0050] The winch apparatus may be configured for use with different types
of spoolable media. For example, the winch assembly may be configured for
use with a synthetic or fibre spoolable media. The winch apparatus may be
configured for use with BOB (Braid Optimised for Bending), Plasma,
Spectra, Dynema or similar like rope structures.

[0051] The winch apparatus may be configured for use in multiple
applications. In some arrangements the winch apparatus may be configured
for use in onshore applications, for example as part of a crane assembly.
In some arrangements the winch apparatus may be configured for use in
offshore applications, for example for use in deploying and recovering
payloads into and from the sea, as part of a crane assembly or the like.

[0052] According to a second aspect of the present invention there is
provided a method of establishing a tension gradient within a spoolable
medium, comprising:

[0053] providing first and second drum assemblies each defining a
discontinuous drum contact surface;

[0054] wrapping a portion of the spoolable medium around the contact
surface of both the first and second drum assemblies; and

[0055] rotating both the first and second drum assemblies about respective
first and second axes of rotation which are inclined relative to each
other.

[0056] The method according to the second aspect may relate to a method of
operating the winch apparatus according to the first aspect. Accordingly,
optional features associated with the second aspect may be assumed to
include any feature, taken in isolation or combination, identified in
relation to the first aspect. For example, the method may comprise
arranging the drum assemblies to intermesh each other, to be side by side
or the like.

[0057] According to a third aspect of the present invention there is
provided a winch system comprising a winch apparatus according to the
first aspect.

[0058] The winch system may comprise a spoolable medium storage
arrangement. The storage arrangement may comprise a spool, basket or the
like. The winch system may comprise a compensator arrangement. The
compensator arrangement may comprise a heave compensator arrangement, for
example to compensate for heaving motion of an offshore vessel upon which
the winch assembly is located.

[0059] Other aspects of the invention may relate to a crane arrangement
which comprises a winch apparatus according to the first aspect.

[0060] Other aspects may relate to a vessel, such as an offshore or
onshore vessel, which comprises a winch apparatus according to the first
aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] These and other aspects of the present invention will now be
described, by way of example only, with reference to the accompanying
drawings, in which:

[0062] FIG. 1 is a perspective view of a winch apparatus according to an
embodiment of the present invention;

[0063] FIG. 2 is a simplified illustration of two separate drum assemblies
of the winch apparatus of FIG. 1, wherein the drum assemblies are shown
separated;

[0064] FIG. 3 is a further simplified illustration of the two separate
drum assemblies of FIG. 6, wherein the drum assemblies are shown in an
intermeshed configuration;

[0065] FIG. 4a is a view of the winch apparatus of FIG. 1 from above;

[0066] FIG. 4b is a diagrammatic representation demonstrating a relative
inclination between two axes of rotation of the winch apparatus in a
vertical plane;

[0067] FIG. 5a is a view of the winch apparatus of FIG. 1 from the front;

[0068] FIG. 5b is a diagrammatic representation of a relative inclination
between two axes of rotation of the winch apparatus in a horizontal
plane;

[0069]FIG. 6 is a view of the winch apparatus of FIG. 1 from above,
showing an engaged spoolable medium;

[0070] FIG. 7 is a diagrammatic representation of the individual tension
gradient applied by each element;

[0071] FIG. 8 is a diagrammatic representation of the interaction between
individual support elements and a spoolable medium;

[0072] FIG. 9 is a perspective view of a winch apparatus in accordance
with an alternative embodiment of the present invention;

[0073] FIG. 10 is a front view of the winch apparatus of FIG. 9;

[0074] FIG. 11 is a top view of the winch apparatus of FIG. 9;

[0075] FIG. 12 is representation of a winch system which incorporates the
winch apparatus of FIG. 1; and

[0076] FIG. 13 is a representation of a winch system which incorporates
the winch apparatus of FIG. 12.

DETAILED DESCRIPTION OF THE DRAWINGS

[0077] A perspective view of a winch apparatus, generally identified by
reference numeral 10, in accordance with an embodiment of the present
invention is shown in FIG. 1. As will be discussed in further detail
below, the winch apparatus 10 is configured as a capstan type winch for
use in operation with a spoolable medium, such as a metal or synthetic
wire, rope, cable or the like.

[0078] The winch apparatus 10 comprises first and second drum assemblies
12, 14 mounted on a common support shaft 16 which is secured to a frame
18. The first drum assembly 12 comprises a plurality of circumferentially
arranged support elements 20 each having discrete contact surfaces which
collectively define a drum contact surface of the first drum assembly 12.
The support elements 20 are arranged with gaps defined therebetween, such
that a discontinuous drum support surface is established. Similarly, the
second drum assembly 14 also comprises a plurality of circumferentially
arranged support elements 22 having individual discrete contact surfaces
which collectively define a drum contact surface of the second drum
assembly 14. The support elements 22 are also arranged with gaps
therebetween, such that a discontinuous drum contact surface is
established. As illustrated, the drum assemblies 12, 14 are arranged such
that the respective support elements 20, 22 are intermeshed. That is, the
support elements 20 of the first drum assembly 12 are arranged in the
gaps defined between the support elements 22 of the second drum assembly
14, and vice versa. Accordingly, the first and second drum assemblies 12,
14 may be arranged to overlap in both axial and radial directions.

[0079] Reference is additionally made to FIG. 2, which provides a
simplified and diagrammatic illustration of the first and second drum
assemblies 12, 14, shown separated for clarity. Each drum assembly 12, 14
is provided generally in the form of a cylindrical cage, with the
respective support elements 20, 22 arranged circumferentially around
respective first and second axes of rotation 24, 26. Each support element
20, 22 is arranged parallel with a respective axis of rotation 24, 26
such that the defined discontinuous drum contact surface of each drum
assembly 12, 14 is also arranged parallel with a respective rotation axis
24, 26. Each support element 22, 24 is generally elongate with opposite
ends of each support element 22, 24 secured via mechanical fasteners 27
to the outer periphery of respective inner support members 28, 30 and
respective outer support members 32, 34. The outer members 28, 30 are
mounted on respective winch flanges 36, 38. Further, each drum assembly
12, 14 comprises a slewing gear ring 40, 42 configured to be engaged by a
drive arrangement comprising multiple individual drive assemblies 44 (see
FIG. 1). In other embodiment a single drive assembly may be provided. The
drive arrangement is configured to rotate each drum assembly 12, 14 about
the respective rotation axes 24, 26 in a synchronous manner. The drive
arrangement may be electric, hydraulic, pneumatic, engine or the like, or
any suitable combination thereof.

[0080] FIG. 3 shows the simplified drum assemblies 12, 14 of FIG. 2
intermeshed to define the complete winch apparatus 10. As illustrated,
the drum assemblies 12, 14 are arranged such that the first and second
axes of rotation 24, 26 are inclined relative to each other, which
results in the discontinuous contact surfaces of each drum assembly 12,
24 also being inclined relative to each other. It should be understood
that the angle of inclination has been exaggerated for purposes of the
present description. As will be discussed in further detail below, this
inclined arrangement of the first and second drum assemblies 12, 14
establishes a preferential path of an associated spoolable medium wrapped
around the winch apparatus 10. A more detailed description of the
relative inclination of the first and second axes of rotation will now be
given with reference to FIGS. 4 and 5.

[0081] Reference is first made to FIG. 4, wherein FIG. 4a shows the winch
apparatus 10 from above, and FIG. 4b provides a simplified illustration
of the relative inclination which demonstrates a relative inclination
between the axes of rotation 24, 26, with the relative inclination
exaggerated for clarity. As illustrated, the drum assemblies 12, 14 are
transversely skewed relative to a vertical plane 45 such that the first
and second rotation axes 24, 26 define a relative inclination angle
αv. In the present exemplary embodiment inclination angle
αv may be in a region between 1 to 3 degrees, for example
around 1.8 degrees. The individual drive assemblies 44 are also clearly
illustrated in FIG. 4a, wherein each drum 14, 16 is engaged to be drive
by two of the drive assemblies 44. Further, each drive assembly 44 is
mounted on the frame 18 in a manner to accommodate the relative
inclination of each drum assembly 12, 14.

[0082] FIG. 5a shows the winch apparatus 10 from the front, and FIG. 5b
provides a simplified illustration of the relative inclination which
demonstrates a relative inclination between the axes of rotation 24, 26,
with the relative inclination exaggerated for clarity. As illustrated,
the drum assemblies 12, 14 are also transversely skewed relative to a
horizontal plane 46 such that the first and second rotation axes 24, 26
define an relative inclination angle αH. In the present
exemplary embodiment inclination angle αH may be in a region
between 1 to 3 degrees, for example around 1.8 degrees.

[0083] It should be noted that both the first and second drum assemblies
12, 14 are rotatably mounted on the common support shaft 16. In this
respect the support shaft may include offset portions configured to
permit rotation of each drum assembly 12, 14 about the first and second
inclined rotation axes.

[0084] Reference is now made to FIG. 6 of the drawings in which the winch
apparatus 10 is shown from above and in use with a spoolable medium 50,
such as a synthetic or fibre rope, such as a BOB (Braid Optimised for
Bending) rope. As shown, the spoolable medium 50 is wrapped a number of
times around each drum assembly 12, 14 with an outboard end 50a extending
from one side of the winch assembly 10, specifically from a defined
outboard take-off point 52, and an inboard end 50b extending from the
opposite side of the winch assembly 10, specifically from a defined
inboard take-off point 54. The outboard end 50a of the spoolable medium
50 may extend to engage a payload, and the inboard end 50b may extend to
a storage location.

[0085] The spoolable medium 50 follows a defined helical path around each
drum assembly 12, 14 between the defined take-off points 52, 54. The
defined helical path and take-off points 52, 54 of the spoolable medium
are established and fixed by the relative inclination of each drum
assembly 12, 14. Accordingly, the requirement for any specific fleeting
arrangements, such as knives or the like, is eliminated.

[0086] In use, the winch apparatus 10 is configured to apply a tension
gradient along the portion of the spoolable medium 50 in contact with the
contact surfaces of the drum assemblies 12, 14. Specifically, the
apparatus 10 creates a tension gradient which reduces the tension in the
spoolable medium from a high tension T1 in the outboard end 50a to a low
tension T2 in the inboard end 50b. This tension gradient may be defined
in accordance with the capstan friction equation defined hereinbefore,
and noted again for convenience:

[0091] This tension gradient may be used to permit appropriate
manipulation of a payload attached to the spoolable medium 50.

[0092] It should be noted that the relative inclination of the drum
assemblies 12, 14 is such that for a single wrap of the spoolable medium
50, half of the spoolable medium is engaged only by the support elements
20 of the first drum assembly 12, and the other half of the spoolable
medium is engaged only by the support elements 22 of the second drum
assembly 14.

[0093] As noted above, each drum assembly 12, 14 comprises a discontinuous
contact surface provided by the spaced apart respective support elements
22, 24. Accordingly, each support element provides a discrete
contribution to the total tension gradient applied across the spoolable
medium, as will be described with reference to FIG. 7 which shows a
cross-sectional view of a single support element 20. The support element
20 includes a curved surface 56 defined by a circular arc which extends
for an arc angle θE defined by the central angle formed by the
end points 58, 60 of the arc surface 56. It should be noted that the drum
contact surface wrap angle defined by the support elements in each drum
assembly 12, 14 totals 360 degrees. This arrangement may permit a
preferential support of the spoolable medium 50 over the collective drum
contact surfaces, which may prevent any kinking or the like of the
spoolable medium 50 across any edge regions of the support elements 20,
22. This arrangement may also permit a preferential support of the
spoolable medium 50 to be permitted while achieving a maximum tension
gradient within the spoolable medium 50 by maximising the available wrap
angle.

[0094] A spoolable medium 50 in contact with the curved surface 56 will
have a high tension outboard end T1E and a lower tension inboard
side T2E, with the tension gradient being determined by:

T 1 E T 2 E = μθ E ##EQU00004##

[0095] Accordingly, the total tension gradient may be a function of the
total contact wrap angle θ (as set out in the capstan friction
equation above), wherein the total contact wrap angle θ is provided
by the sum of the individual arc angles θE of the support
elements 20, 22. That is:

θ=ΣθE

[0096] The provision of the total tension gradient in individual discrete
portions over the separate support elements 20, 22 may permit more
control over the tension gradient in the spoolable medium 50.
Furthermore, this arrangement may permit a required tension gradient to
be ensured over a minimum length of the spoolable medium 50. Accordingly,
high resolution de-tensioning may be achieved by applying many small
points of contact providing a proportionally small variance in tension
differential. Thus, changes in length, relative movement, work and the
like are minimised to mitigate frictional heat generated in the spoolable
medium 50. Tension may therefore be removed or added in many small
accurately controlled linear steps as opposed to a low quantity of large
steps as present in prior art systems. This arrangement provides a kind
method of working the spoolable medium 50 to provide longer life and
operate the spoolable medium 50 in its natural form without applying
excessive external forces.

[0097] Reference is now made to FIG. 8 which shows a number of adjacent
support elements 20 in cross-section, engaged with the spoolable medium
50. In this embodiment the facing edges of the arc shaped surfaces of
adjacent elements 20 are arranged tangentially to each other. This
arrangement permits the spoolable medium to extend tangentially between
adjacent support elements 20, thus achieving complete contact with each
individual surface 56 and preventing any adverse kinking or the like of
the spoolable medium as it leaves one support element and arrives at an
adjacent support element.

[0098] FIG. 8 also clearly illustrates the gap arrangement between
adjacent support elements 20. This gap arrangement provides the
respective discontinuous drum contact surfaces. Also, providing the
support elements with gaps therebetween permits the support elements to
be positioned to define a desired effective drum radius 62, for example
which is appropriate to the particular spoolable medium 50, and at the
same time provide the necessary overall wrap angle to achieve a suitable
tension gradient while minimising the actual contact surface area.
Furthermore, the provision of gaps between support elements may provide
advantages in terms of cooling, drainage and the like.

[0099] Referring again to FIG. 1, each drum assembly 12, 14 comprises an
associated braking arrangement 13, 15 configured to providing friction
braking to the drum assemblies 12, 14. However, in alternative
embodiments, the drive assemblies 44 may alternatively, or additionally,
be configured to provide braking.

[0100] A winch apparatus in accordance with a second embodiment of the
present invention will now be described with reference to FIGS. 9, 10 and
11. The winch apparatus, generally identified by reference numeral 110,
is similar to the apparatus 10 first shown in FIG. 1 and as such like
features share like reference numerals, incremented by 100.

[0101] Referring initially to FIG. 9, the apparatus 110 comprise a first
and second drum assemblies 112, 114 which are mounted on a frame 118 and
arranged to be separated in a radial direction, and to overlap in an
axial direction. Each drum assembly 12, 114 is arranged to be engaged by
a spoolable medium 150 to establish an outboard end 150a at a high
tension T1, and an inboard end 150b at a lower tension T2.

[0102] As shown in FIGS. 10 and 11, the first and second drum assemblies
112, 114 are mounted on the frame 118 to be inclined relative to each
other. This relative inclination arrangement permits the spoolable medium
150 to follow a set and predefined helical path around each drum assembly
112, 114, and also to set the respective outboard and inboard take-off
points 152, 154.

[0104] The exemplary embodiments described herein may be used in a number
of applications and environments. For example, the apparatuses 10, 110
may be used in onshore applications, for example in crane arrangements or
the like. Further, the apparatuses 10, 110 may be used in marine
environments, for example in offshore vessels, such as ships, oil rigs or
the like. For example, the apparatuses 10, 110 may be used in
applications for deploying and retrieving payloads to and from the sea.

[0105] The exemplary embodiments may also be used in combination with
further equipment suited for the appropriate use. An example of such a
combination of equipment is shown in FIG. 12, reference to which is now
made.

[0106] The exemplary arrangement of FIG. 12 reflects an offshore
application and includes the winch apparatus 10 first shown in FIG. 1. In
addition to the winch apparatus 10, the arrangement includes an
overboarding assembly 200 which is used to appropriately direct a
spoolable medium 50 (shown in broken outline) from a vessel (not shown)
into the sea. Additionally, a heave compensator 202 is provided which
provides dynamic compensation to the spoolable medium 50 to accommodate
for heaving motion of the associated vessel. Further, the arrangement of
FIG. 12 includes a track tensioner arrangement 204 which is configured to
apply a degree of tension to an inboard side of the spoolable medium
which extends from the winch apparatus 10. The track tensioner 204 may be
used to apply a desired inboard tension in the spoolable medium 50 which
permits an appropriate outboard tension to be accommodated, for example.
The arrangement shown in FIG. 12 further includes a storage arrangement
in the form of a storage basket 206 which permits the spoolable medium to
be stored in a zero tension state.

[0107] The arrangement in FIG. 13 also reflects an offshore application
and in this example includes the winch apparatus 110 first shown in FIG.
9. The arrangement shown may include the same components as those of FIG.
13, such as the heave compensator 202. However, in the present
arrangement the inboard end of the spoolable medium 150 is spooled to and
from a winch drum 208, which may provide storage for the spoolable medium
150, and also establish a required degree of tension within the inboard
end of the spoolable medium.

[0108] It should be understood that the embodiments described herein are
merely exemplary and that various modifications may be made thereto
without departing from the scope of the present invention.